30. Mammalian development Flashcards

1
Q

What is considered day 0?

A

Fertilisation

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2
Q

What happens at day 1?

A

First cleavage

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3
Q

What happens at day 2?

A

2 cell stage then 4 cell stage

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4
Q

What happens from days 3-4?

A

8 cell stage

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5
Q

What happens at day 4?

A

Compacted morula

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6
Q

What is formed at day 5?

A

Early blastocyte

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7
Q

What is formed at day 6-7?

A

Late stage blastocyte (hatching)

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8
Q

What happens at day 8-9?

A

Implantation of the blastocyte

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9
Q

Why is there no yolk in mammal eggs?

A

Because all the nutrients the embryo requires are provided by the mother

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10
Q

What does the first cleavage produce?

A

Produces blastomeres that are developmentally equivalent (holoblastic cleavage)

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11
Q

What directions are the first and second cleavage?

A

First cleavage is a vertical cleavage

Second cleavage is one vertical and one horizontal

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12
Q

Why do cells become smaller with each division?

A

For the restoration of the nuclear to cytoplasm ratio

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13
Q

What happens with the activation of the embryo genome?

A
  • Destruction of pre-stored mRNA

- But pre-stored proteins may continue to function and regulate development for some time

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14
Q

What is cadherin?

A

A calcium dependent cell adhesion molecule

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15
Q

What does cadherin do?

A

Mediates adhesion between blastomeres

- Cell outlines coalesce to form a morula

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16
Q

What does the cleavage of blastomeres result in?

A

Some cells enclosed within the inner compartment of the morula

17
Q

What is cavitation?

A

What fluid begins to accumulate between blastomeres

18
Q

What does cavitation result in the formation of?

A

A blastocoel

19
Q

What is the outer layer of cells in the blastomeres?

A

The trophoblast/trophectoderm

20
Q

What does the trophectoderm give rise to?

A

The placenta

21
Q

What are the inner cells of the blastulation known as?

A

The inner cell mass

22
Q

What does the inner cell mass give rise to?

A

The embryo

23
Q

What is the purpose of the zona?

A
  • The zona prevents cell-cell contact of the embryo and the oviduct wall so that there is no premature hatching
  • Premature hatching causes a tubal pregnancy
24
Q

What happens during zona hatching?

A
  • Hatching occurs in the uterus just before implantation

- Blastocyst secretes proteases that weaken the zona so that it implants to the uterine epithelium

25
What are the changes in physiology of the embryo during the preimplantation period?
Embryo switches to using glucose rather than pyruvate
26
How does the zygote generate energy?
Generates energy from low levels of oxidation of pyruvate and/or lactate with aspartate (and other amino acids).
27
What does the blastocysts generate energy from?
Both aerobic glycolysis and the oxidation of glucose
28
What is the morula defined as?
Once an embryo has compacted and formed tight junctions between blastomeres, the embryos is known as a morula
29
How is the zona digested during zona hatching?
- Apical proteases (and uterine proteases) digest the glycoprotein zona pellucida - The hatched blastocyst is free to implant into the endometrium of the uterus
30
What does Na/K ATPase activity on the basolateral membrane result in?
An ionic gradient is formed and water flows into the embryo through aquaporins
31
What are the exchanges during Na/K ATPase activity?
3 Na go in and 2K go out, water goes in
32
What are the three phases of implantation?
Apposition, attachment and invasion
33
What happens in the attachment phase?
- Loss of zona and glycocalyx | - Vascular changes
34
What cells directly contact the uterus during attachment?
- Trophoblast directly contacts uterine epithelium | - Trophoblast cells start to penetrate epithelium
35
What happens after the adhesion phase of embryo implantation?
- Trophoblast cells penetrate uterine epithelium, decidua and up to a third of myometrium - Target maternal blood vessels and degrade them to provide adequate blood supply to growing foetus and placenta